I'll be honest, I think the reason people love this show is because of Byeon Woo-Seok's portrayal of Sun-jae. The fact that he's very attractive, tall, and is generally likeable makes this show nice to watch, lol. The love story itself is interesting, but there's a few things I think the show did a poor job at.
1. I WISH that we got a richer back story on all the characters
2. I wish more things tied the ML and FL together besides the FL's ability to go back in time. Maybe if they had known each other since childhood rather than high school? Idk. I just feel like the relationship itself sort of lacked depth.
3. It would have been nice if the themes of class or poverty or something substantial were highlighted. Casting such attractive characters is great but I wish the producers/writers also put more thought into adding more complexity to this plot.
4. The person who was trying to hurt Im Sol -- wish we had background on him? Like if the reason he wanted to hurt was for revenge idk I just feel like it was a weird plot twist that made no sense to me. I wanted MORE! ?

I like the relationship between the leads, I think the love story itself is nice, Sun-jae is a good bf, etc etc. But I just wanted more. There's 1000s of romantic storylines, but very few are able to have substance and unfortunately, as adorable the couple is, thats kind of the extent of what makes this show memorable. Their on-screen chemistry made me want to continue watching and it got me hooked on the show for a bit, but that's about it sadly.
Great songs though, 10/10.